As shown in FIG. 1, a known pilot valve includes a valve body 1 within which four spools 4 are slidably disposed to establish and interrupt communication between an inlet port 2 and an outlet port 3. Cylindrical guides 5 are fit in the valve body 1 in a coaxial relation to the spools 4. Retainers 6 are pressed toward the lower surface of the cylindrical guides 5 by primary springs 7. This causes pistons 8 to slidably move up within the cylindrical guides 5. Springs 9 are used to hold the spools 4 in a piston to interrupt communication between the inlet port 2 and the outlet port 3. A plate 10 is placed on the valve body 1 and has an opening 11. A universal joint 12 has a base portion 12a which extends through the opening 11 for threaded engagement with the upper portion of the valve body 1. A top portion 12b of the universal joint 12 has a mounting shaft 13 and a disk 14. A lever 15 is mounted to the mounting shaft 13. When the lever 15 is pivotally moved in forward, rearward, leftward and rightward directions, the disk presses down either one of the two pistons or both pistons 5. This causes the spools 4 to move in a direction to establish communication between the inlet and outlet ports. Oil under pressure then flows from the inlet port 2 to the outlet port 3 through oil holes 4a of the spools 4.
With such a pilot valve, the universal joint 12 is used to pivot the lever 15 in forward, rearward, leftward and rightward directions relative to the valve body 1. The universal joint 12 per se is complicated in structure, requires a number of parts, and is expensive. The overall size of the pilot valve can not be reduced since the universal joint is quite large.
In addition, when the lever 15 is operated, the retainers 6 come into contact with steps 16 of the valve body 1 to limit stroke of the lever 15. The pistons 8 and the retainers 6 thus function as a stopper and are subject to heavy loads. In order to improve durability, the retainers 6 and the pistons 8 must be made lager and made of expensive and high quality materials. This results in an increase in the size and cost of the overall pilot valve.